(1) Field of the Invention
The present invention relates to a digital broadcast receiving apparatus, and in particular to a receiving apparatus for receiving and displaying data such as image data which has been subjected to digital compression.
(2) Related Art
In recent years, digital broadcasts which transmit video and audio data via transmission means such as satellites and CATVs (Community Antenna Televisions) have been performed.
Research into still image information providing services, where a plurality of inter-related still images are transmitted using a digital broadcast and users performs interactive operations to view their desired still images out of the plurality of still images, has also been performed.
The following is a description of the operation for using such a still image information providing service, with reference to FIG. 1.
FIG. 1 shows an operation image for selecting a still image.
When the xe2x80x9cSERVICE MENUxe2x80x9d still image 11 is displayed and a user selects the xe2x80x9c4, WEATHER FORECASTxe2x80x9d item, the xe2x80x9cWEATHER FORECASTxe2x80x9d still image 12 is displayed.
The following is a description of a conventional technique for providing this still image information providing service, with reference to FIGS. 1-3.
FIG. 2 shows a representation of still image data transmitted from a digital broadcast transmitting apparatus.
The digital broadcast transmitting apparatus repeatedly transmits compressed data of a plurality of still images.
The drawing shows a state where the first still image is the xe2x80x9cSERVICE MENUxe2x80x9d still image 11 and the seventh still image is the xe2x80x9cWEATHER FORECASTxe2x80x9d still image 12, among the data 20 of 150 still images which is transmitted repeatedly.
FIG. 3 is a block diagram showing the structure of the conventional digital broadcast receiving apparatus 100.
The conventional digital broadcast receiving apparatus 100 receives data transmitted from a digital broadcast transmitting apparatus and displays still images according to operations made by the user. The conventional digital broadcast receiving apparatus 100 includes the tuner and demodulator 102, the transport decoder 103, the local memory 104, the MPEG (Moving Picture Experts Group) decoder 105, the local memory 106, the CPU 109 for controlling each unit of the apparatus according to an operation made by the user, and the main memory 110.
The tuner and demodulator 102 receives data 101 transmitted from the digital broadcast transmitting apparatus according to a station selecting operation, such as a selecting operation of a satellite, made by the user, demodulates the received data 101, and inputs the demodulated data into the transport decoder 103.
The transport decoder 103 separates and extracts a transport stream indicated by the CPU 109 from the data inputted from the tuner and demodulator 102.
Note that the transmitted data 101 is transport streams which are obtained by subjecting a plurality of coded streams to a time-division multiplexing using packets of relatively short fixed length.
There are several stream types of the transport streams, such as xe2x80x9cimagexe2x80x9d, xe2x80x9caudioxe2x80x9d, and xe2x80x9cdataxe2x80x9d.
When the stream type is xe2x80x9cimagexe2x80x9d or xe2x80x9caudioxe2x80x9d, the transport decoder 103 inputs picture or audio data of this transport stream into the MPEG decoder 105, and the MPEG decoder 105 expands the picture or audio data and display the expanded picture or audio data. It should be noted here that in this specification, pictures include still images and video images.
When the stream type is xe2x80x9cdataxe2x80x9d, the transport decoder 103 stores the data of the xe2x80x9cdataxe2x80x9d transport stream in the local memory 104 attached to the transport decoder 103. The data stored in the local memory 104 can be accessed by the CPU 109.
The conventional digital broadcast receiving apparatus 100 expands and displays still image data transmitted from the digital broadcast transmitting apparatus as the xe2x80x9cimagexe2x80x9d stream type using the MPEG decoder 105. Not all still images that have been transmitted are displayed, with only one out of the transmitted still image being displayed according to a selecting operation made by the user. More specifically, the CPU 109 controls the MPEG decoder 105 according to the selecting operation made by the user so as to freeze the display state when a selected still image is displayed. When the CPU 109 does not perform a specific control, a plurality of pieces of still image data which have been transmitted repeatedly are inputted into the MPEG decoder 105 and the MPEG decoder 105 displays all still images repeatedly like video images.
The conventional digital broadcast transmitting apparatus transmits still images as the xe2x80x9cimagexe2x80x9d stream type and data concerning relations among still images as the xe2x80x9cdataxe2x80x9d stream type to allow the digital broadcast receiving apparatus 100 to perform the above process.
The data concerning relations among still images is information indicating relations among still images using identifiers assigned to each still image. This data indicates, for instance, that the xe2x80x9cSERVICE MENUxe2x80x9d still image 11 and the xe2x80x9cWEATHER FORECASTxe2x80x9d still image 12 in FIG. 1 are related to each other. The data concerning relations among still images is hereinafter called still image relation data.
In the digital broadcast receiving apparatus 100, the transport decoder 103 stores the still image relation data transmitted from the digital broadcast transmitting apparatus in the local memory 104. The CPU 109 accesses the local memory 104 and stores the still image relation data in the main memory 110.
The transport decoder 103 inputs compressed still image data transmitted from the digital broadcast transmitting apparatus into the MPEG decoder 105 via the compressed data stream input port 107.
The MPEG decoder 105 includes the serial-parallel conversion circuit 111 for converting a data signal inputted from the transport decoder 103 into an 8-bit parallel signal, the AV decoder 113 for expanding picture and audio data stored in the local memory 106 and storing the expanded data in the local memory 106, and the display circuit 114 for displaying the expanded data stored in the local memory 106.
Therefore, compressed still image data inputted into the MPEG decoder 105 is stored in the local memory 106, is expanded by the AV decoder 113, is stored back into the local memory 106, and is displayed by the display circuit 114. It should be noted here that the display by the MPEG decoder 105 means the output of signals for TV output. On receiving an operation made by the user, the CPU 109 refers to the still image relation data stored in the main memory 110, obtains the identifier of the still image selected by the user, and instructs the MPEG decoder 105 to display the still image of the identifier and to freeze the display screen when the still image is displayed.
When the still image 11 in FIG. 1 is displayed and the user selects the xe2x80x9c4. WEATHER FORECASTxe2x80x9d item, for instance, the CPU 109 obtains the identifier of the still image corresponding to the xe2x80x9c4. WEATHER FORECASTxe2x80x9d item by referring to the main memory 110, informs the MPEG decoder 105 of the obtained identifier, and instructs the MPEG decoder 105 to display the still image 12 and to freeze the display screen at the state where the still image 12 is displayed.
On receiving this instruction from the CPU 109, the MPEG decoder 105 checks the compressed still image data that is transmitted thereafter and freezes the display state when the still image 12 is displayed.
In this manner, the conventional digital broadcast receiving apparatus 100 allows the user to view necessary still images by performing interactive operations.
However, there is a problem that the conventional digital broadcast receiving apparatus takes a long time to display still images selected by the user.
When data of 150 still images is repeatedly transmitted from the digital broadcast transmitting apparatus, for instance, there is a time lag of up to the time necessary to send the data of all 150 still images between the time when the user selects a still image and the time when the selected still image is displayed. If five seconds are necessary to transmit the data of 150 still images, the user has to wait up to five seconds to see the selected still image.
The object of the present invention is to provide a digital broadcast receiving apparatus which realizes a still image information providing service with a good response, that is, which increases the probability that a still image selected by a user will be displayed at high speed.
The above object is achieved by a digital broadcast receiving apparatus for receiving a plurality of pieces of still image data which are repeatedly transmitted from a digital broadcast transmitting apparatus and for displaying a still image selected by a user, the receiving apparatus including: a storage unit; a receiving unit for sequentially receiving the plurality of pieces of still image data; a prediction unit for predicting at least one piece of still image data which is likely to be specified by the user before the user specifies the piece of still image data; a still image fetching unit for fetching, into the storage unit, every piece of still image data that has been predicted by the prediction unit out of the plurality of pieces of still image data received by the receiving unit; an operation accepting unit for accepting a selecting operation of a still image by the user, the selecting operation specifying a piece of still image data corresponding to the selected still image; and a display unit for processing the specified piece of still image data out of the still image data in the storage unit and for displaying a still image according to the processed still image data.
With the above structure, when a plurality of pieces of still image data are transmitted from the digital broadcast transmitting apparatus, the digital broadcast receiving apparatus of the present invention receives the plurality of pieces of still image data, predicts at least one piece of still image data which is likely to be selected by the user, and stores the predicted still image data in the storage unit prior to the selecting operation made by the user, thereby increasing the probability that a still image selected by the user will be displayed at high speed.
In the digital broadcast receiving apparatus, the receiving unit may further receive link information and store the link information in the storage unit, the link information showing which still images are selectable by the user during a display of each still image, and the prediction unit may predict at least one piece of still image data which is likely to be specified by the user by referring to the link information stored in the storage unit.
With the above structure, the digital broadcast receiving apparatus of the present invention receives information showing which still images can be selected by the user while a still image is being displayed, that is, link information showing link relations among still images. Still image data which should be stored in the storage unit can be predicted by referring to the link information so that, for instance, data of non-linked still images does not need to be stored in the storage unit, reducing the storage capacity in the storage unit for storing still image data.
In the digital broadcast receiving apparatus, the prediction unit may refer to the link information and a still image currently being displayed, and predict at least one piece of still image data which is likely to be specified in a following selecting operation.
With the above structure, on recognizing a still image selected by the user, the digital broadcast receiving apparatus of the present invention predicts still images which are likely to be selected by the user in the next selecting operation or other next selecting operations by referring to the link information.
Therefore, still image data is stored in the storage unit beforehand according to the prediction, thereby increasing probability that a still image selected by the user will be displayed at high speed. Also, prediction of still images which are likely to be selected by the user minimizes the number of pieces of still image data that need to be stored in advance to realize rapid display of still images. As a result, capacity in the storage unit for storing still image data can be minimized.
In the digital broadcast receiving apparatus, the operation accepting unit may accept the selecting operation by the user even while the still image fetching unit is fetching still image data into the storage unit. The prediction unit may invalidate a result of a previous prediction when a still image selected by the user has been displayed by the display unit as a result of the selecting operation accepted by the operation accepting unit, and commence a new prediction. The still image fetching unit, when the operation accepting unit accepts the selecting operation and still image data specified by the selecting operation has not been stored in the storage unit, may fetch the specified still image data in the storage unit, and, when the prediction unit invalidates the result of the previous prediction and commences the new prediction, may fetch newly predicted still image data into the storage unit.
With the above structure, the digital broadcast receiving apparatus commences a new prediction on receiving a selecting operation made by the user so that still image data to be stored in the storage unit beforehand is specified according to the current state. Therefore, even if the storage capacity for storing still image data is small, probability that a still image selected by the user will be displayed at high speed can be increased.
In the digital broadcast receiving apparatus, the still image data transmitted from the digital broadcast transmitting apparatus may be subjected to digital compression and the display unit may include: a display data storage unit for storing data to be displayed; an expansion unit for expanding still image data; and an image display unit for displaying an image according to the data stored in the display data storage unit, where the display unit expands still image data specified by the user using the expansion unit, stores the expanded still image data in the display data storage unit, and displays a still image according to the expanded still image data using the image display unit.
With the above structure, when still image data transmitted from the digital broadcast transmitting apparatus has been subjected to digital compression, the digital broadcast receiving apparatus can store compressed still image data predicted by the prediction unit as it is, prior to a display selecting operation made by the user. As a result, the storage capacity in the storage unit can be minimized.
In the digital broadcast receiving apparatus, the expansion unit may execute a computer program to expand still image data specified by the user and the still image data may be transmitted with picture data from the digital broadcast transmitting apparatus, the picture data and the still image data being to be superimposed and displayed. The digital broadcast receiving apparatus may further includes a picture receiving unit for receiving the picture data. The display unit may further include a transfer control unit for performing the first transfer for transferring the expanded still image data to the display data storage unit and the second transfer for transferring the received picture data to the displayed data storage unit by arbitrating between the first transfer and the second transfer. The transfer control unit may include: a transfer necessity detection unit for detecting whether the first transfer is necessary and detecting whether the second transfer is necessary; a transfer authorization unit for giving exclusively a transfer authorization to either of the first transfer and the second transfer; and a transfer performing unit for performing either of the first transfer and the second transfer which has been detected as being necessary and has been given the transfer authorization by the transfer authorization unit. When the transfer necessity detection unit detects that one of the first transfer and the second transfer is necessary, the transfer authorization unit gives the transfer authorization to the one of the first transfer and the second transfer; when both of the first transfer and the second transfer are detected as being necessary, the transfer authorization unit gives the transfer authorization to the first of the first transfer and the second transfer to be detected as being necessary; and when neither the first transfer nor the second transfer is detected as being necessary, the transfer authorization unit gives the transfer authorization to the first transfer.
With the above structure, the digital broadcast receiving apparatus can expand and display compressed still image data without using the AV decoder of the MPEG decoder. Therefore, even if the MPEG decoder has only one AV decoder, the MPEG decoder can expand compressed data of other pictures or audio and can superimpose and display the still image and the other pictures.
Also, the digital broadcast receiving apparatus can arbitrate between received still image data and other picture data for data transfer to the display data storage memory and gives the transfer authorization to the still image data when neither still image data nor other picture data needs to be transferred. Therefore, when still image data needs to be transferred, transfer of the still image data can be commenced without requesting the transfer authorization, so that this digital broadcast receiving apparatus is optimal for the case where still images need to be displayed at high speed even if the other pictures are deteriorated to a degree.
In the digital broadcast receiving apparatus, the image display unit may include a transfer unit for transferring still image data specified by the user from the storage unit to the expansion unit. The transfer unit includes: an input buffer for temporarily holding n pieces of inputted 8-bit data (n being an integer no less than 2); a CPU, which handles n bytes as one word, for fetching the still image data specified by the user from the storage unit and storing the fetched still image data in the input buffer n bytes at a time; a counter for counting either of from 0 to (nxe2x88x921) and from (nxe2x88x921) to 0; an output order storage unit for storing a value showing a counting order of the counter beforehand; a data selection unit for selecting one out of the n pieces of 8-bit data stored in the input buffer according to a value of the counter; and a data output unit for transferring the 8-bit data selected by the data selection unit to the expansion unit.
Because the digital broadcast receiving apparatus has the above structure, the CPU can fetch still image data in word units from the main memory and input the fetched still image data into the MPEG decoder even when the AV decoder of the MPEG decoder can only process 8-bit parallel data. As a result, the still image data can be transferred at high speed, in comparison with the case where the CPU transfers the still image data in byte units.
In the digital broadcast receiving apparatus, the link information may be repeatedly transmitted from the digital broadcast transmitting apparatus, and the receiving unit may receive the link information and stores the link information into the storage unit only once.
With the above structure, once the digital broadcast receiving apparatus stores the link information showing link relations among still images in the storage unit, still images which are likely to be selected by the user can be predicted by referring to the link information. Therefore, the link information does not need to be sequentially stored in the storage unit.
In the digital broadcast receiving apparatus, the link information may be composed of a plurality of pieces of link data which each are related to one piece of the still image data and show which still images are selectable by the user during a display of a still image according to the piece of still image data, the plurality of pieces of link data may be repeatedly transmitted from the digital broadcast transmitting apparatus, the receiving unit may receive the plurality of pieces of link data transmitted from the digital broadcast transmitting apparatus and sequentially stores the plurality of pieces of link data in the storage unit, and the prediction unit may predict at least one piece of still image data which is likely to be specified in a next selecting operation, by referring to one out of the plurality of pieces of link data related to data of a still image currently being displayed.
With the above structure, the link information is composed of a plurality of pieces of link data. Therefore, the digital broadcast receiving apparatus can predict still images which are likely to be selected next by the user while a still image is being displayed using at least one of the plurality of pieces of link data. As a result, the digital broadcast receiving apparatus can perform this prediction even if the storage capacity in the storage unit is small.
The above object is also achieved by a digital broadcast receiving apparatus for receiving a plurality of pieces of still image data which have been subjected to digital compression and are repeatedly transmitted from a digital broadcast transmitting apparatus and for outputting an image signal for displaying a still image selected by a user, the receiving apparatus including: a storage unit; a receiving unit for sequentially receiving the plurality of pieces of still image data; a prediction unit for predicting at least one piece of still image data which is likely to be specified by the user; a still image fetching unit for fetching, into the storage unit, every piece of still image data that has been predicted by the prediction unit out of the plurality of pieces of still image data received by the receiving unit; an operation accepting unit for accepting a selecting operation of a still image by the user, the selecting operation specifying a piece of still image data corresponding to the selected still image; and an expansion output unit for expanding the specified still image data out of the still image data in the storage unit and for outputting an image signal of the expanded still image data.
With the above structure, when a plurality of pieces of still image data is transmitted from the digital broadcast transmitting apparatus, the digital broadcast receiving apparatus receives the plurality of pieces of still image data, predicts at least one piece of still image data which is likely to be selected by the user, and stores the predicted still image data in the storage unit prior to a selecting operation made by the user, thereby increasing the probability that an image signal of a still image selected by the user will be outputted at high speed.
In the digital broadcast receiving apparatus, the receiving unit may further receive link information and store the link information in the storage unit, the link information showing which still images are selectable by the user while an image signal of each still image is being outputted, and the prediction unit may predict at least one piece of still image data which is likely to be specified by the user, by referring to the link information stored in the storage unit.
With the above structure, the digital broadcast receiving apparatus of the present invention receives information concerning which still image can be selected by the user while an image signal of a still image is being outputted, that is, link information showing link relations among still images. Still image data which should be stored in the storage unit can be predicted by referring to the link information so that, for instance, data of non-linked still images does not need to be stored in the storage unit, reducing the storage capacity in the storage unit for storing still image data.
The above object is further achieved by a digital broadcast receiving apparatus for receiving the first type data and the second type data transmitted from a digital broadcast transmitting apparatus and for outputting signals according to the first type data and the second type data, the receiving apparatus including: a signal output unit for outputting a signal according to inputted data; a receiving unit for receiving data including the first type data and the second type data; the first extracting unit for extracting the first type data out of the data received by the receiving unit; the second extracting unit for extracting the second type data out of the data received by the receiving unit; and a transfer control unit for performing the first transfer for transferring the first type data from the first extracting unit to the signal output unit and for performing the second transfer for transferring the second type data for the second extracting unit to the signal output unit by arbitrating between the first transfer and the second transfer. The transfer control unit may include: a transfer necessity detection unit for detecting whether the first transfer is necessary and detecting whether the second transfer is necessary; a priority information storage unit for storing priority information showing which of the first transfer and the second transfer has transfer priority; a transfer authorization unit for giving exclusively a transfer authorization to either of the first transfer and the second transfer; and a transfer performing unit for performing either of the first transfer and the second transfer which has been detected as being necessary and has been given the transfer authorization by the transfer authorization unit. When the transfer necessity detection unit detects that one of the first transfer and the second transfer is necessary, the transfer authorization unit gives the transfer authorization to the one of the first transfer and the second transfer; when both of the first transfer and the second transfer are detected as being necessary, the transfer authorization unit gives the transfer authorization to the first of the first transfer and the second transfer to be detected as being necessary; and when neither the first transfer nor the second transfer is detected as being necessary, the transfer authorization unit gives the transfer authorization to either of the first transfer and the second transfer by referring to the priority information.
With the above structure, the digital broadcast receiving apparatus can control data transfer according to importance of data when received data is to be expanded and outputted. Also, the transfer priority can be given to the still image data during arbitration between still image data transfer and picture data transfer, increasing the probability that a still image selected by the user will be displayed at high speed.
In the digital broadcast receiving apparatus, the first type data may be graphics data for displaying graphics, the second type data may be video data for displaying video images, the priority information stored in the priority information storage unit may show that transfer of the graphics data has the transfer priority, the transfer authorization unit may give the transfer authorization to the first transfer when the transfer necessity detection unit detects that neither the first transfer nor the second transfer is necessary, and the signal output unit may output an image signal for images where graphics and video images are superimposed according to inputted graphics data and video data.
With the above structure, the digital broadcast receiving apparatus can display graphics, such as a program table, at high speed and can display video images behind the graphics.